An hour later, eager enthusiasts can bid on an 1874 $20 Double Eagle coin. The fundraiser will support the San Francisco Museum and Historical Society's goal of renovating a second mint and developing an on-site museum, according to a news release from Kagin's Inc., the numistmatic firm that appraised the 1,427 coins' collective worth to be more than $10 million.

"The family loved the idea that these coins could help in the effort to restore the building where most of the Saddle Ridge Hoard coins were made," said David McCarthy, senior numismatist at Kagin's, in an announcement.

The couple, identified by Kagin's as John and Mary, were walking their dog when they spotted the edge of a rusty can peeking from out of the moss in February 2013. The discovery spawned a whirlwind of claims by people citing alleged family ties and theories about who had the coins, such as outlaw Jesse James.

A total of 1,312 coins were struck at the Old Mint, Kagin's said.

After the auction, much of the gold cache will be available for sale on Amazon with bidding prices starting at $2,575. Wagers for the most expensive coin, an 1866-S Double Eagle without the "In God We Trust" motto, starts at $1.2 million. Kagin's will host a live sale of the coins, too.

Part of the stash will be available for sale online at 9 p.m. PDT.

But not all the coins will be available for sale. The couple who found the gold treasure will keep a few pieces as keepsakes.